The anticipated legislation could serve as a companion to a similar House bill.

Senators are working on a bill that could extend the life of a controversial chemical security program, but details still remain under wraps.

The Senate Homeland Security Committee was to mark up what it is calling the "Protecting American Chemical Facilities from Attack Act of 2014" on June 25, but consideration of the measure was ultimately deleted, without explanation, from the agenda of a committee business meeting that day.

A spokeswoman for the panel, which is chaired by Senator Tom Carper (D-Del.), declined to provide details regarding the legislation and how soon it might be unveiled.

Carper's committee held a hearing on the Homeland Security Department's Chemical Facility Anti-Terrorism Standards on May 14. During the hearing, Carper said a bill approved in April by the House Homeland Security Committee could serve "as a model for [his panel's] work on this issue between now and the end of the year."

The House legislation is backed by DHS officials, largely because it would provide multiyear authorization for a program that thus far has been renewed annually through the congressional appropriations process. DHS officials have said uncertainty stemming from year-to-year renewals has made it more difficult to regulate chemical facilities.

The House bill does not include provisions that would give the department the authority to require specific security upgrades at facilities. So-called "inherently safer technology" requirements are favored by labor union officials, environmentalists and some Democrats, but are opposed by Republicans and industry officials.

The House legislation would also continue an exemption for water treatment facilities that has been criticized by some Democrats and activist groups. An interagency report released by the Obama administration last month urged Congress to end the exemption.

Carper, during the May 14 hearing, did not indicate whether a Senate bill might include additional provisions meant to address any of these controversies, but he did acknowledge some of the CFATS program's perceived shortcomings.

Last year's fatal explosion at a fertilizer plant in West, Texas "showed that, in some cases, the Department likely isn't aware of some facilities that should be submitting information to the program but are not," Carper said.

The nonpartisan Government Accountability Office "and other experts have also expressed concern that the department's method for assessing risk for a chemical facility is incomplete," Carper noted.